Ha! Not wanting to alarm you, and you shouldn't be if the bike is running well.... You may be a clean livin' guy, but gonna tell you the intakes in my '06 Project Bike looked the same after 90k. The insides were a different story.... I'm not sure I'm a fan of RingFree, the OP had used it constantly, but rode like grandma (shifted gears at 3500, bike didn't even see the power band (5000 up). RingFree is unlike anything I've seen, it has a high content of some kind of oil. I would think that oil might contribute to carbon build-up, and the insides of this head and pistons was on the oily side. I don't think RingFree will rid an engine of carbon, as won't most injection cleaners... further measures are required.
What happens with carbon build-up on the intakes is it doesn't allow the valves to seat/seal properly, so you lose compression. This can cause hot starting problems and if worse, colder starting problems. To diagnose, do a compression test on a warm engine, and if low, do a leakdown test (compressed air into the spark plug holes with a fitting) and see if leaking back past the intakes. One could also stick a borescope down the spark plug holes and see what build-up is on the pistons, and if you have one with a mirror attachment, can perhaps get an idea of what's on the intakes.
One would think valve clearances would grow in that case, but they don't seem to (perhaps cancelled out by normal wear). It would be interesting to compare valve check reading history and shim changes over the life of the bike.
IF carboned up, without disassembly to manually remove the carbon, one can on a hot engine at high idle, remove airbox and spray water directly into the throttle bodies, which turns to steam and will lift carbon... may have to repeat a few times. Valve clearances will then definitely get smaller, potentially to the point of no clearance (no carbon, valve seats deeper), likely having to repeat valve checks until you find them stable (I would do the water treatment each of these times). One can also use say Gumout combustion chamber cleaner which will have solvents (and perhaps some water) to accomplish the same thing applied similarly to my "water injection" method (used in the old days).
So, I'll always say don't ride like grandma, get the bike into the power band once in a while (the horsepower only really starts kicking in at 4500+, full HP at 7000), but what you want is a 'clean burn' as well, so perhaps not "full bore WOT acceleration" either (mixture richened by ECU to get all that power).
Riding like grandma does not give you a clean burn as the engine is loaded, underperforming for what it is, call it lugging with richened fuel mixture, and over time........ say no more. Note, exhaust valves are relatively clean as they run hotter than anything in there.
I can say that at 37k miles my '04 had stuck piston rings and I guarantee you that the engine lived life over 5,000 rpm with abrupt, large throttle openings every time it left the garage. Yamaha regularly promotes RingFree for their boat engines and the bottles are sized to treat boat fuel tanks. Some Gen I and Gen II engines would suddenly have Fast Starter Syndrome and not start and they had low compression readings. Treating the engine like it had carbon buildup or stuck rings would fix the problem.
